Problem: $ { \left[\begin{array}{rrr}{-2} & {0} & {1} \\ {-1} & {3} & {3}\end{array}\right]+\left[\begin{array}{rrr}{3} & {4} & {0} \\ {0} & {-1} & {1}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-2}+{3} & {0}+{4} & {1}+{0} \\ {-1}+{0} & {3}+{-1} & {3}+{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {4} & {1} \\ {-1} & {2} & {4}\end{array}\right]}$